From cbe0d2fffc7698b5652d0e0786fdc656cbd589de Mon Sep 17 00:00:00 2001
From: Simon Frei <freisim93@gmail.com>
Date: Wed, 17 Jun 2020 10:03:39 +0200
Subject: [PATCH] lib/db: Improve error message on meta inconsistency (#6751)

---
 lib/db/lowlevel.go |  7 ++++++-
 lib/db/meta.go     | 11 ++++++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/lib/db/lowlevel.go b/lib/db/lowlevel.go
index fe3ec685a..557dc49b4 100644
--- a/lib/db/lowlevel.go
+++ b/lib/db/lowlevel.go
@@ -811,7 +811,12 @@ func (db *Lowlevel) getMetaAndCheck(folder string) *metadataTracker {
 func (db *Lowlevel) loadMetadataTracker(folder string) *metadataTracker {
 	meta := newMetadataTracker()
 	if err := meta.fromDB(db, []byte(folder)); err != nil {
-		l.Infof("No stored folder metadata for %q; recalculating", folder)
+		if err == errMetaInconsistent {
+			l.Infof("Stored folder metadata for %q is inconsistent; recalculating", folder)
+		} else {
+			l.Infof("No stored folder metadata for %q; recalculating", folder)
+
+		}
 		return db.getMetaAndCheck(folder)
 	}
 
diff --git a/lib/db/meta.go b/lib/db/meta.go
index 5f682898f..e7cabb7fa 100644
--- a/lib/db/meta.go
+++ b/lib/db/meta.go
@@ -8,6 +8,7 @@ package db
 
 import (
 	"bytes"
+	"errors"
 	"math/bits"
 	"time"
 
@@ -15,6 +16,8 @@ import (
 	"github.com/syncthing/syncthing/lib/sync"
 )
 
+var errMetaInconsistent = errors.New("inconsistent counts detected")
+
 type countsMap struct {
 	counts  CountsSet
 	indexes map[metaKey]int // device ID + local flags -> index in counts
@@ -104,7 +107,13 @@ func (m *metadataTracker) fromDB(db *Lowlevel, folder []byte) error {
 	if err != nil {
 		return err
 	}
-	return m.Unmarshal(bs)
+	if err = m.Unmarshal(bs); err != nil {
+		return err
+	}
+	if m.counts.Created == 0 {
+		return errMetaInconsistent
+	}
+	return nil
 }
 
 // countsPtr returns a pointer to the corresponding Counts struct, if